<?php
//dezend by http://www.yunlu99.com/ QQ:270656184
defined('BASEPATH') || exit('No direct script access allowed');
class CI_Session_database_driver extends CI_Session_driver implements SessionHandlerInterface
{
	/**
	 * DB object
	 *
	 * @var	object
	 */
	protected $_db;
	/**
	 * Row exists flag
	 *
	 * @var	bool
	 */
	protected $_row_exists = false;
	/**
	 * Lock "driver" flag
	 *
	 * @var	string
	 */
	protected $_platform;

	public function __construct(&$params)
	{
		parent::__construct($params);
		$CI = &get_instance();
		isset($CI->db) || $CI->load->database();
		$this->_db = $CI->db;

		if (!$this->_db instanceof CI_DB_query_builder) {
			throw new Exception('Query Builder not enabled for the configured database. Aborting.');
		}
		else if ($this->_db->pconnect) {
			throw new Exception('Configured database connection is persistent. Aborting.');
		}
		else if ($this->_db->cache_on) {
			throw new Exception('Configured database connection has cache enabled. Aborting.');
		}

		$db_driver = $this->_db->dbdriver . (empty($this->_db->subdriver) ? '' : '_' . $this->_db->subdriver);

		if (strpos($db_driver, 'mysql') !== false) {
			$this->_platform = 'mysql';
		}
		else if (in_array($db_driver, array('postgre', 'pdo_pgsql'), true)) {
			$this->_platform = 'postgre';
		}

		if (!isset($this->_config['save_path']) && $this->_config['save_path'] = config_item('sess_table_name')) {
			log_message('debug', 'Session: "sess_save_path" is empty; using BC fallback to "sess_table_name".');
		}
	}

	public function open($save_path, $name)
	{
		if (empty($this->_db->conn_id) && !$this->_db->db_connect()) {
			return $this->_fail();
		}

		return $this->_success;
	}

	public function read($session_id)
	{
		if ($this->_get_lock($session_id) !== false) {
			$this->_db->reset_query();
			$this->_session_id = $session_id;
			$this->_db->select('data')->from($this->_config['save_path'])->where('id', $session_id);

			if ($this->_config['match_ip']) {
				$this->_db->where('ip_address', $_SERVER['REMOTE_ADDR']);
			}

			if (!($result = $this->_db->get()) || (($result = $result->row()) === NULL)) {
				$this->_row_exists = false;
				$this->_fingerprint = md5('');
				return '';
			}

			$result = ($this->_platform === 'postgre' ? base64_decode(rtrim($result->data)) : $result->data);
			$this->_fingerprint = md5($result);
			$this->_row_exists = true;
			return $result;
		}

		$this->_fingerprint = md5('');
		return '';
	}

	public function write($session_id, $session_data)
	{
		$this->_db->reset_query();
		if (isset($this->_session_id) && ($session_id !== $this->_session_id)) {
			if (!$this->_release_lock() || !$this->_get_lock($session_id)) {
				return $this->_fail();
			}

			$this->_row_exists = false;
			$this->_session_id = $session_id;
		}
		else if ($this->_lock === false) {
			return $this->_fail();
		}

		if ($this->_row_exists === false) {
			$insert_data = array('id' => $session_id, 'ip_address' => $_SERVER['REMOTE_ADDR'], 'timestamp' => time(), 'data' => $this->_platform === 'postgre' ? base64_encode($session_data) : $session_data);

			if ($this->_db->insert($this->_config['save_path'], $insert_data)) {
				$this->_fingerprint = md5($session_data);
				$this->_row_exists = true;
				return $this->_success;
			}

			return $this->_fail();
		}

		$this->_db->where('id', $session_id);

		if ($this->_config['match_ip']) {
			$this->_db->where('ip_address', $_SERVER['REMOTE_ADDR']);
		}

		$update_data = array('timestamp' => time());

		if ($this->_fingerprint !== md5($session_data)) {
			$update_data['data'] = $this->_platform === 'postgre' ? base64_encode($session_data) : $session_data;
		}

		if ($this->_db->update($this->_config['save_path'], $update_data)) {
			$this->_fingerprint = md5($session_data);
			return $this->_success;
		}

		return $this->_fail();
	}

	public function close()
	{
		return $this->_lock && !$this->_release_lock() ? $this->_fail() : $this->_success;
	}

	public function destroy($session_id)
	{
		if ($this->_lock) {
			$this->_db->reset_query();
			$this->_db->where('id', $session_id);

			if ($this->_config['match_ip']) {
				$this->_db->where('ip_address', $_SERVER['REMOTE_ADDR']);
			}

			if (!$this->_db->delete($this->_config['save_path'])) {
				return $this->_fail();
			}
		}

		if ($this->close() === $this->_success) {
			$this->_cookie_destroy();
			return $this->_success;
		}

		return $this->_fail();
	}

	public function gc($maxlifetime)
	{
		$this->_db->reset_query();
		return $this->_db->delete($this->_config['save_path'], 'timestamp < ' . (time() - $maxlifetime)) ? $this->_success : $this->_fail();
	}

	protected function _get_lock($session_id)
	{
		if ($this->_platform === 'mysql') {
			$arg = md5($session_id . ($this->_config['match_ip'] ? '_' . $_SERVER['REMOTE_ADDR'] : ''));

			if ($this->_db->query('SELECT GET_LOCK(\'' . $arg . '\', 300) AS ci_session_lock')->row()->ci_session_lock) {
				$this->_lock = $arg;
				return true;
			}

			return false;
		}
		else if ($this->_platform === 'postgre') {
			$arg = 'hashtext(\'' . $session_id . '\')' . ($this->_config['match_ip'] ? ', hashtext(\'' . $_SERVER['REMOTE_ADDR'] . '\')' : '');

			if ($this->_db->simple_query('SELECT pg_advisory_lock(' . $arg . ')')) {
				$this->_lock = $arg;
				return true;
			}

			return false;
		}

		return parent::_get_lock($session_id);
	}

	protected function _release_lock()
	{
		if (!$this->_lock) {
			return true;
		}

		if ($this->_platform === 'mysql') {
			if ($this->_db->query('SELECT RELEASE_LOCK(\'' . $this->_lock . '\') AS ci_session_lock')->row()->ci_session_lock) {
				$this->_lock = false;
				return true;
			}

			return false;
		}
		else if ($this->_platform === 'postgre') {
			if ($this->_db->simple_query('SELECT pg_advisory_unlock(' . $this->_lock . ')')) {
				$this->_lock = false;
				return true;
			}

			return false;
		}

		return parent::_release_lock();
	}
}

?>
